Abstract
The maximization of the mixing entropy with the optimal range of enthalpy in high-entropy alloys (HEAs) can promote the formation of a stable single solid-solution phase with the absence of competing intermetallic compounds. The resultant effects, such as lattice distortion, can contribute to excellent mechanical properties, which has motivated numerous efforts to develop and design single-phase HEAs. However, challenges still remain, particularly on quantifying the lattice distortion and relating it to materials properties. In this study, we have developed a NbTaTiV refractory HEA with a single body-centered-cubic (BCC) structure using an integrated experimental and theoretical approach. The theoretical efforts include thermodynamic modeling, i.e., CALculation of PHAse Diagram (CALPHAD). The microstructural evolutions have been investigated by systematic heat-treatment processes. The typical dendrite microstructure was observed, which is caused by the elemental segregation during the solidification in the as-cast condition. The structural inhomogeneity and chemical segregation were completely eliminated by the proper homogenization treatment at 1200 °C for 3 days. The homogeneous elemental distribution was quantitatively verified by the Atom Probe Tomography (APT) technique. Importantly, results indicate that this HEA exhibits the high yield strength and ductility at both room and high temperatures (up to 900 °C). Furthermore, the effects of the high mixing entropy on the mechanical properties are discussed and quantified in terms of lattice distortions and interatomic interactions of the NbTaTiV HEA via first-principles calculations. It is found that the local severe lattice distortions are induced, due to the atomic interactions and atomic-size mismatch in the homogenization-treated NbTaTiV refractory HEA.
| Original language | English |
|---|---|
| Pages (from-to) | 158-172 |
| Number of pages | 15 |
| Journal | Acta Materialia |
| Volume | 160 |
| DOIs | |
| State | Published - Nov 2018 |
Funding
The research is supported by the U.S. Army Office Project (W911NF-13-1-0438) with the program managers, Michael P. Bakas and David M. Stepp, and the material was developed. Peter K. Liaw also thanks the support from the National Science Foundation (DMR-1611180 and 1809640) with the program director, Gary Shiflet and Diana Farkas, and the neutron work was conducted. C. Lee would like to acknowledge the partial support from the Center of Materials Processing with Prof. Claudia Rawn as the director, a Tennessee Higher Education Commission (THEC) Center of Excellence located at The University of Tennessee, Knoxville. The CALPHAD modeling work was carried out to support the Cross-Cutting Technologies Program at the National Energy Technology Laboratory (NETL) — Strategic Center for Coal, managed by Robert Romanosky (Technology Manager) and Charles Miller (Technology Monitor). The research was executed through the NETL's Office of Research and Development's Innovative Process Technologies (IPT) Field Work Proposal. Research performed by the AECOM staff was conducted under the RES contract, DE-FE-0004000. The APT measurements were performed as a part of a user proposal at the ORNL's Center for the Nanophase Materials Science (CNMS), which is a DOE Office of Science User Facility (JDP and WG). A portion of research at the ORNL's Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. The first-principles research is also supported by the City University of Hong Kong (Grant No. 9610336), National Natural Science Foundation of China (NSFC) (Grant No. 11605148), and Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. CityU 21202517) Disclaimer: The computational-modeling work presented in the paper was funded by the Department of Energy, National Energy Technology Laboratory, an agency of the United States Government, through a support contract with AECOM. Neither the United States Government nor any agency thereof, nor any of their employees, nor AECOM, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. The research is supported by the U.S. Army Office Project ( W911NF-13-1-0438 ) with the program managers, Michael P. Bakas and David M. Stepp, and the material was developed. Peter K. Liaw also thanks the support from the National Science Foundation ( DMR-1611180 and 1809640 ) with the program director, Gary Shiflet and Diana Farkas, and the neutron work was conducted. C. Lee would like to acknowledge the partial support from the Center of Materials Processing with Prof. Claudia Rawn as the director, a Tennessee Higher Education Commission (THEC) Center of Excellence located at The University of Tennessee, Knoxville. The CALPHAD modeling work was carried out to support the Cross-Cutting Technologies Program at the National Energy Technology Laboratory (NETL) — Strategic Center for Coal, managed by Robert Romanosky (Technology Manager) and Charles Miller (Technology Monitor). The research was executed through the NETL's Office of Research and Development's Innovative Process Technologies (IPT) Field Work Proposal. Research performed by the AECOM staff was conducted under the RES contract, DE-FE-0004000. The APT measurements were performed as a part of a user proposal at the ORNL's Center for the Nanophase Materials Science (CNMS), which is a DOE Office of Science User Facility (JDP and WG). A portion of research at the ORNL's Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. The first-principles research is also supported by the City University of Hong Kong (Grant No. 9610336 ), National Natural Science Foundation of China (NSFC) (Grant No. 11605148 ), and Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. CityU 21202517 ) Disclaimer: The computational-modeling work presented in the paper was funded by the Department of Energy, National Energy Technology Laboratory, an agency of the United States Government, through a support contract with AECOM. Neither the United States Government nor any agency thereof, nor any of their employees, nor AECOM, nor any of their employees, makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
Keywords
- First-principles calculation
- High-entropy alloy
- In-situ neutron diffraction
- Lattice distortion